Betta Color Genetics
Need a basic introduction to genetics? Read this: https://basicbiology.net/micro/genetics/genetic-inheritance
How color works in domestic bettas:
The color on each fish comes from four types of unique, pigment producing cells. These cells are found in layers:
Images of each color (If I can find them) will be presented in a gallery at the bottom of each section.
Do note if an expression is dominant whether homozygous or heterozygous, the second gene that "doesn't matter" (So to say) will be represented by "__"
- Iridescent Layer / Blue Layer (Top Layer) made up of Iridocytes
- Black Layer - made up of Melanocytes
- Red Layer - made up of Erythrocytes
- Yellow Layer (Bottom Layer) made up of Xanthocytes
Images of each color (If I can find them) will be presented in a gallery at the bottom of each section.
Do note if an expression is dominant whether homozygous or heterozygous, the second gene that "doesn't matter" (So to say) will be represented by "__"
Iridescent / Blue Layer
In this layer there are three genes to consider.
Blue Color
There are three colors of blue (which may vary in richness, but all blues are one of the following) and this gene exhibits incomplete dominance:
Spread
This gene controls the density and distribution of iridrocytes on the fish's body. More iridrocytes = more blue/more iridescence. It exhibits complete dominance.
Non Blue
As of this moment, there is no gene that has been identified that causes no blue or iridescence to be expressed. However, as there are indeed fish that exhibit no blue or even the slightest shimmer of iridescence, there is likely such a gene.
A note:
The richness of the blue present can be due to the layer of black below. More black causing darker colors, no black causing more pastel colors.
Blue Color
There are three colors of blue (which may vary in richness, but all blues are one of the following) and this gene exhibits incomplete dominance:
- Turquoise - BlBl
- This is the "dominant" coloration, a blue-green color (If a betta appears green, it is actually turquoise). It requires two dominant blue alleles.
- Royal Blue - Blbl
- This coloration is the result of the incomplete dominance mentioned previously. It is a dark rich blue.
- Steel Blue - blbl
- This color is a grey-blue and is the "recessive" coloration as it requires two recessive alleles.
Spread
This gene controls the density and distribution of iridrocytes on the fish's body. More iridrocytes = more blue/more iridescence. It exhibits complete dominance.
- Full Spread - Si __
- Color should be expanded to cover most, if not all of the fish (Often excepting the head). This is the dominant Allele.
- "Normal" or "Wild" Spread - sisi
- Reduction of color, often just a shimmer, creates ray-like projections into the fins and "dots" along the body. This is the recessive allele.
- Steel blue with this kind of spread can appear silver
- Reduction of color, often just a shimmer, creates ray-like projections into the fins and "dots" along the body. This is the recessive allele.
Non Blue
As of this moment, there is no gene that has been identified that causes no blue or iridescence to be expressed. However, as there are indeed fish that exhibit no blue or even the slightest shimmer of iridescence, there is likely such a gene.
A note:
The richness of the blue present can be due to the layer of black below. More black causing darker colors, no black causing more pastel colors.
Blue Phenotypes - mouse over or click on each photo to see the name of each coloration
Black Layer
Again there are three genes to consider with this layer.
Black Color (Melano)
I'm a little iffy on how this one works. As far as I know this gene exhibits complete dominance. But this is my understanding:
Some sources say that M creates black pigment, while m is a mutant that creates the melanistic. I honestly can't figure it out. I wouldn't be surprised if there were multiple alleles though.
Cambodian
This is a recessive gene that creates a lack of black pigment and a lighter body than fins.
Bright/Blond
This gene creates a reduction in black pigment (Though not always an absence of black), resulting in a lighter color. It is responsible for pastels, bright reds, and smokey/grey blacks. It is also recessive.
A note:
Most of these are best seen on red fish, as that is the layer below this. However it can also affect the layers above it, much as if you were to cut out a shape in one paper, cover it with another, and hold it up to a window. The cut out areas are lighter than the dark, despite you not changing the top layer.
Black Color (Melano)
I'm a little iffy on how this one works. As far as I know this gene exhibits complete dominance. But this is my understanding:
- "Normal" Black - M___
- This is the dominant coloration. It creates a solid black layer that is not melanistic. Or potentially a fish without black.
- Melano Black - mm
- This is the recessive coloration. It creates melanistic (Completely black) bettas. Females will be infertile
Some sources say that M creates black pigment, while m is a mutant that creates the melanistic. I honestly can't figure it out. I wouldn't be surprised if there were multiple alleles though.
Cambodian
This is a recessive gene that creates a lack of black pigment and a lighter body than fins.
- Non-Cambodian - C__
- This means that there is no change in coloration
- Cambodian - cc
- This causes the loss of black pigment and lightening of body
Bright/Blond
This gene creates a reduction in black pigment (Though not always an absence of black), resulting in a lighter color. It is responsible for pastels, bright reds, and smokey/grey blacks. It is also recessive.
- Non-Blond - B__
- There is no change in coloration
- Blond - bb
- The black pigment is lightened, creating a brighter color.
A note:
Most of these are best seen on red fish, as that is the layer below this. However it can also affect the layers above it, much as if you were to cut out a shape in one paper, cover it with another, and hold it up to a window. The cut out areas are lighter than the dark, despite you not changing the top layer.
Black Phenotypes - mouse over or click on each photo to see the name of each coloration
Red Layer
In this layer we have four genes to consider.
Extended Red
This gene controls the amount of red present on a fish. It functions similarly to the spread gene mentioned in the blue layer (And so personally I think it would be better termed "Red Extension" or something... but whatever).
Red Loss
This is similar greying hair in mammals, in that it is the loss of color that the creature is born with.
Reduced Red
This gene creates a restriction of the red to the fins, leaving a different colored body. The gene, however, has not been identified and so, other than the phenotype, we do not know how it works.
Non-Reds
These genes create fish that do not show any red pigment, but it is however created by the red layer. These are recessive and there are multiple alleles.
A note:
Red is the bottom layer, and so these genes are often not seen by us, but this does not mean that they do not carry it.
Extended Red
This gene controls the amount of red present on a fish. It functions similarly to the spread gene mentioned in the blue layer (And so personally I think it would be better termed "Red Extension" or something... but whatever).
- Extended Red - R__
- This causes the body and fins to be entirely red, similar to the full spread.
- Less Red - rr
- This causes the expression of less red distribution. *I am not actually sure what this phenotype looks like*
Red Loss
This is similar greying hair in mammals, in that it is the loss of color that the creature is born with.
- Red Loss - Rl__
- Causes loss of red pigment, resulting in a flesh-y color
- No Loss - rlrl
- Coloration is not changed
Reduced Red
This gene creates a restriction of the red to the fins, leaving a different colored body. The gene, however, has not been identified and so, other than the phenotype, we do not know how it works.
Non-Reds
These genes create fish that do not show any red pigment, but it is however created by the red layer. These are recessive and there are multiple alleles.
- Normal expression - NRNR
- This means there is no change to the coloration
- Yellow - nr1nr1
- There are two categories of this yellow phenotype as well:
- Type 1 = A light yellow
- Type 2 = A golden yellow
- There is also another variant known as pineapple
- It may be caused by the expression of nr1 over a fully extended red. It appears as a neon yellow with black edges on the scales.
- There are two categories of this yellow phenotype as well:
- Orange - nr2nr2
- This causes an orange fish
- This is a relatively new allele. An interesting thing about this allele is that, while a rich pumpkin-color is desired, the more orange x orange crosses that are preformed in a line, the more washed out the color becomes.
- This causes an orange fish
A note:
Red is the bottom layer, and so these genes are often not seen by us, but this does not mean that they do not carry it.
Red Phenotypes - mouse over or click on each photo to see the name of each coloration
Yellow Layer
There is still a lot of debate about whether this is even actually a layer. Because of this, I'll list it, but you've got to go do your own research. You probably won't find much.
Some Sources call it a Cellophane layer. I like this better, honestly, since the yellow comes from the red layer. The "white" you see on "koi" bettas is often this layer showing (because all layers above it are inhibited). It can appear yellow-ish or orange-ish, hence the name "yellow layer", I think. I am not quite sure why this happens. The other time you may see this layer is when a fish is growing new tissue on the edge of its fins, you may see a "clear" layer of fin which will eventually produce the other pigment producing cells, this is the cellophane
Some Sources call it a Cellophane layer. I like this better, honestly, since the yellow comes from the red layer. The "white" you see on "koi" bettas is often this layer showing (because all layers above it are inhibited). It can appear yellow-ish or orange-ish, hence the name "yellow layer", I think. I am not quite sure why this happens. The other time you may see this layer is when a fish is growing new tissue on the edge of its fins, you may see a "clear" layer of fin which will eventually produce the other pigment producing cells, this is the cellophane
Fin color modifiers
As far as I know, these are present over all layers
Variegated Fins
These fish are commonly labelled as "Butterfly Bettas" as if it's a fin shape or breed. This is wrong, it is simply a coloration (I think it's similar to the whole paint vs pinto thing in horses).
This gene is dominant, and creates white at the edge of the fins. How much white there is is highly variable, it can be anything from the thinnest rim to the entire fin. The ideal amount of white (Supposedly) Is 50/50 white and color.
Black Lace
These fish are kind of like the inverse of those with variegated fins, instead of a rim of white, they have a rim of black on their tails. Some sources say that this is actually the phenotype of MM/Mm in the black layer, a fertile black. As I mentioned in that section, I have found too many conflicting sources to figure out what's what. I actually can't even find any sources saying whether black lace is dominant or recessive. Expression may also vary like the Variegated Fins.
A note: I think Melano Black may be the "Solid Black" and "Black Lace" (Fertible black?) May be "Transparent Black" but while this explains the difference between blacks and fertility, it does not explain the Black Lace effect similar to the Variegated Fins.
It is possible it confused Melano Black with Fertile Black/Black Lace (?) If the Melano has clear edges due to variegation. It is also possible to layer black lace and variegation, and the variegation appears to be dominant
Variegated Fins
These fish are commonly labelled as "Butterfly Bettas" as if it's a fin shape or breed. This is wrong, it is simply a coloration (I think it's similar to the whole paint vs pinto thing in horses).
This gene is dominant, and creates white at the edge of the fins. How much white there is is highly variable, it can be anything from the thinnest rim to the entire fin. The ideal amount of white (Supposedly) Is 50/50 white and color.
- Variegated Fins - Vf__
- The dominant phenotype, white is present
- Non-Variegated Fins - vfvf
- The recessive phenotype, no white is present
Black Lace
These fish are kind of like the inverse of those with variegated fins, instead of a rim of white, they have a rim of black on their tails. Some sources say that this is actually the phenotype of MM/Mm in the black layer, a fertile black. As I mentioned in that section, I have found too many conflicting sources to figure out what's what. I actually can't even find any sources saying whether black lace is dominant or recessive. Expression may also vary like the Variegated Fins.
A note: I think Melano Black may be the "Solid Black" and "Black Lace" (Fertible black?) May be "Transparent Black" but while this explains the difference between blacks and fertility, it does not explain the Black Lace effect similar to the Variegated Fins.
It is possible it confused Melano Black with Fertile Black/Black Lace (?) If the Melano has clear edges due to variegation. It is also possible to layer black lace and variegation, and the variegation appears to be dominant
Fin Modified Color Phenotypes - mouse over or click on each photo to see the name of each coloration
Body Color Modifiers
Marble
This gene is very interesting! It was originally found by a prison inmate who was breeding fish, and it functions by turning the different layers of pigment producing cells on and off at random because it is a transposon. More detail here: https://bettasource.com/more-betta/genetics/pattern/breeding-marbles
This gene is partially dominant, and it very unpredictable in its expression.
A note: Marbled fish change a lot when they are young, and may settle into an appearance once they finish growing, but because of the location of the pigment cells, it is possible for fish to change color even later in life
Terminology
For some reason, the fish industry decided to come up with fancy names for specific variations of marbled fish, rather than just calling them marbled.
Dalmatian
This is a relatively new gene that I can't find a lot on. It seems it is definite spots of color, not patches, but only on the fins of the fish. It can easily be confused with a marble that displays spots, but a marble with small spots will likely have spots on the body, which a true Dalmatian will not have. I also believe it only appears with an orange base and red spots. This may change, however.
This gene is very interesting! It was originally found by a prison inmate who was breeding fish, and it functions by turning the different layers of pigment producing cells on and off at random because it is a transposon. More detail here: https://bettasource.com/more-betta/genetics/pattern/breeding-marbles
This gene is partially dominant, and it very unpredictable in its expression.
- Very Marbled Fish - MbMb
- This may be more like the "Koi" bettas you see. Highly spotted.
- Moderately Marbled Fish - Mbmb
- Some spots, patchy
- Solid Non-Marbled Fish - mbmb
- No spots
A note: Marbled fish change a lot when they are young, and may settle into an appearance once they finish growing, but because of the location of the pigment cells, it is possible for fish to change color even later in life
Terminology
For some reason, the fish industry decided to come up with fancy names for specific variations of marbled fish, rather than just calling them marbled.
- Fancy - A marbled fish with 3 or more colors visible
- Nemo - A marbled fish with orange, red, and black visible
- Galaxy - A marbled fish that has distinct scales of iridescence (Blue)
- Tiger - A marbled fish with yellow and black (Or blue)
- Candy - A marbled fish with black, red, and blue (Or yellow)
- Samurai - A marbled fish of any color with dragon scaling
Dalmatian
This is a relatively new gene that I can't find a lot on. It seems it is definite spots of color, not patches, but only on the fins of the fish. It can easily be confused with a marble that displays spots, but a marble with small spots will likely have spots on the body, which a true Dalmatian will not have. I also believe it only appears with an orange base and red spots. This may change, however.
Body Modified Color Phenotypes (Multicolor) - mouse over or click on each photo to see the name of each coloration
Below is how Crow has changed colors just since I got him
Opaque
This is an odd one. It's a gene, but it's tightly tied to a coloration. The actual gene is partially dominant (Written as Op)
An Opaque fish will have:
Pastel
These fish have the same set of requirements as Opaque fish, but they often have only one copy of the opaque gene, meaning they aren't as white. Often, to achieve a color, breeds may choose to forgo one of the previously mentioned genes.
Dragonscale
This gene also produces white (Only on the body, I believe), but it comes from crossing fish with other species. It produces thick scales in the iridescent layer that may be metallic in appearance. However, it comes with a number of possible defects, and fish with dragonscale can actually have scales that grow over(?) their eyes as they age, causing them to go blind. I can't find any information on the dominance of this gene.
A note: Many of the breeders of these fish focus intensely on color, and ignore the "proper" physical characteristics of the fish, so many have poor finagle or body shape.
Copper
This is another gene that was produced by outcrossing to other betta species. Like the dragonscale, it modifies the iridescent layer. It is a dominant gene, and displayed using "Nm" (Which means non-metallic, as the "original" coloration is nonmetallic (and recessive))
Mustard Gas
This is not a result of a specific gene, though it is often talk about as if it is. It is simply a bicolor fish, blue and yellow, and it happens to breed true (Consider the nature of those two colors) (Occasionally black appears on the edges of the fins as well, again consider the previously mentioned genetics)
Chocolate
This is also not a specific gene, and is another bicolor fish. It is the result of black and yellow coloration. (Some say Nr-1, some say pineapple).
This is an odd one. It's a gene, but it's tightly tied to a coloration. The actual gene is partially dominant (Written as Op)
An Opaque fish will have:
- Any shade of blue with full spread
- Steel Blue (blbl) is preferred, as it is the lightest of the blues, and other blues may have a green (turquoise) or blue (royal blue) sheen
- Cambodian gene (And whatever makes non-black. Still not clear on it)
- Non-Red genes in the red layer
- At least one copy of the opaque gene (Two preferred, as that increases the expression)
Pastel
These fish have the same set of requirements as Opaque fish, but they often have only one copy of the opaque gene, meaning they aren't as white. Often, to achieve a color, breeds may choose to forgo one of the previously mentioned genes.
Dragonscale
This gene also produces white (Only on the body, I believe), but it comes from crossing fish with other species. It produces thick scales in the iridescent layer that may be metallic in appearance. However, it comes with a number of possible defects, and fish with dragonscale can actually have scales that grow over(?) their eyes as they age, causing them to go blind. I can't find any information on the dominance of this gene.
A note: Many of the breeders of these fish focus intensely on color, and ignore the "proper" physical characteristics of the fish, so many have poor finagle or body shape.
Copper
This is another gene that was produced by outcrossing to other betta species. Like the dragonscale, it modifies the iridescent layer. It is a dominant gene, and displayed using "Nm" (Which means non-metallic, as the "original" coloration is nonmetallic (and recessive))
- Copper - Nm__
- Copper is displayed in the iridescent layer
- Non-Copper - nmnm
- Normal iridescent is displayed
Mustard Gas
This is not a result of a specific gene, though it is often talk about as if it is. It is simply a bicolor fish, blue and yellow, and it happens to breed true (Consider the nature of those two colors) (Occasionally black appears on the edges of the fins as well, again consider the previously mentioned genetics)
Chocolate
This is also not a specific gene, and is another bicolor fish. It is the result of black and yellow coloration. (Some say Nr-1, some say pineapple).
Body Modified Color Phenotypes (Solids(Kinda)) - mouse over or click on each photo to see the name of each coloration
References upon request